The present invention is directed to measuring the quality of communication signals, and more specifically to a method and apparatus for measuring characteristics of a communication signal modulated by a video signal, such as a composite video signal, which is transmitted from one location to another, such as by a cable television (CATV) system.
Existing methods for measuring the quality of a communication signal modulated with a composite video signal in CATV systems require the use of a device connected to the channel that synchronizes to the composite video signal to identify a vertical blanking interval (VBI) where no visual carrier modulation occurs. Such a device is quite costly and cumbersome.
It is desirable to measure the quality of a signal, such as communication signal modulated with a composite video signal in a CATV system, in the presence of modulation, without the need for a synchronizing device.